[PATCH net-next v5 03/19] mm: Make the page_frag_cache allocator use multipage folios

From: David Howells
Date: Thu Apr 06 2023 - 05:44:07 EST

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Change the page_frag_cache allocator to use multipage folios rather than
groups of pages. This reduces page_frag_free to just a folio_put() or
put_page().

Signed-off-by: David Howells <dhowells@xxxxxxxxxx>
cc: "David S. Miller" <davem@xxxxxxxxxxxxx>
cc: Eric Dumazet <edumazet@xxxxxxxxxx>
cc: Jakub Kicinski <kuba@xxxxxxxxxx>
cc: Paolo Abeni <pabeni@xxxxxxxxxx>
cc: Jens Axboe <axboe@xxxxxxxxx>
cc: Jeroen de Borst <jeroendb@xxxxxxxxxx>
cc: Catherine Sullivan <csully@xxxxxxxxxx>
cc: Shailend Chand <shailend@xxxxxxxxxx>
cc: Felix Fietkau <nbd@xxxxxxxx>
cc: John Crispin <john@xxxxxxxxxxx>
cc: Sean Wang <sean.wang@xxxxxxxxxxxx>
cc: Mark Lee <Mark-MC.Lee@xxxxxxxxxxxx>
cc: Lorenzo Bianconi <lorenzo@xxxxxxxxxx>
cc: Matthias Brugger <matthias.bgg@xxxxxxxxx>
cc: AngeloGioacchino Del Regno <angelogioacchino.delregno@xxxxxxxxxxxxx>
cc: Keith Busch <kbusch@xxxxxxxxxx>
cc: Jens Axboe <axboe@xxxxxx>
cc: Christoph Hellwig <hch@xxxxxx>
cc: Sagi Grimberg <sagi@xxxxxxxxxxx>
cc: Chaitanya Kulkarni <kch@xxxxxxxxxx>
cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
cc: Matthew Wilcox <willy@xxxxxxxxxxxxx>
cc: netdev@xxxxxxxxxxxxxxx
cc: linux-arm-kernel@xxxxxxxxxxxxxxxxxxx
cc: linux-mediatek@xxxxxxxxxxxxxxxxxxx
cc: linux-nvme@xxxxxxxxxxxxxxxxxxx
cc: linux-mm@xxxxxxxxx
---
drivers/net/ethernet/google/gve/gve_main.c | 11 +--
drivers/net/ethernet/mediatek/mtk_wed_wo.c | 15 +--
drivers/nvme/host/tcp.c | 7 +-
drivers/nvme/target/tcp.c | 5 +-
include/linux/gfp.h | 1 +
include/linux/mm_types.h | 13 +--
mm/page_frag_alloc.c | 101 +++++++++++----------
7 files changed, 65 insertions(+), 88 deletions(-)

diff --git a/drivers/net/ethernet/google/gve/gve_main.c b/drivers/net/ethernet/google/gve/gve_main.c
index 57ce74315eba..b2fc1a3e6340 100644
--- a/drivers/net/ethernet/google/gve/gve_main.c
+++ b/drivers/net/ethernet/google/gve/gve_main.c
@@ -1263,17 +1263,10 @@ static void gve_unreg_xdp_info(struct gve_priv *priv)

static void gve_drain_page_cache(struct gve_priv *priv)
{
- struct page_frag_cache *nc;
int i;

- for (i = 0; i < priv->rx_cfg.num_queues; i++) {
- nc = &priv->rx[i].page_cache;
- if (nc->va) {
- __page_frag_cache_drain(virt_to_page(nc->va),
- nc->pagecnt_bias);
- nc->va = NULL;
- }
- }
+ for (i = 0; i < priv->rx_cfg.num_queues; i++)
+ page_frag_cache_clear(&priv->rx[i].page_cache);
}

static int gve_open(struct net_device *dev)
diff --git a/drivers/net/ethernet/mediatek/mtk_wed_wo.c b/drivers/net/ethernet/mediatek/mtk_wed_wo.c
index 69fba29055e9..6ce532217777 100644
--- a/drivers/net/ethernet/mediatek/mtk_wed_wo.c
+++ b/drivers/net/ethernet/mediatek/mtk_wed_wo.c
@@ -286,7 +286,6 @@ mtk_wed_wo_queue_free(struct mtk_wed_wo *wo, struct mtk_wed_wo_queue *q)
static void
mtk_wed_wo_queue_tx_clean(struct mtk_wed_wo *wo, struct mtk_wed_wo_queue *q)
{
- struct page *page;
int i;

for (i = 0; i < q->n_desc; i++) {
@@ -298,12 +297,7 @@ mtk_wed_wo_queue_tx_clean(struct mtk_wed_wo *wo, struct mtk_wed_wo_queue *q)
entry->buf = NULL;
}

- if (!q->cache.va)
- return;
-
- page = virt_to_page(q->cache.va);
- __page_frag_cache_drain(page, q->cache.pagecnt_bias);
- memset(&q->cache, 0, sizeof(q->cache));
+ page_frag_cache_clear(&q->cache);
}

static void
@@ -320,12 +314,7 @@ mtk_wed_wo_queue_rx_clean(struct mtk_wed_wo *wo, struct mtk_wed_wo_queue *q)
skb_free_frag(buf);
}

- if (!q->cache.va)
- return;
-
- page = virt_to_page(q->cache.va);
- __page_frag_cache_drain(page, q->cache.pagecnt_bias);
- memset(&q->cache, 0, sizeof(q->cache));
+ page_frag_cache_clear(&q->cache);
}

static void
diff --git a/drivers/nvme/host/tcp.c b/drivers/nvme/host/tcp.c
index 42c0598c31f2..76f12ac714b0 100644
--- a/drivers/nvme/host/tcp.c
+++ b/drivers/nvme/host/tcp.c
@@ -1323,12 +1323,7 @@ static void nvme_tcp_free_queue(struct nvme_ctrl *nctrl, int qid)
if (queue->hdr_digest || queue->data_digest)
nvme_tcp_free_crypto(queue);

- if (queue->pf_cache.va) {
- page = virt_to_head_page(queue->pf_cache.va);
- __page_frag_cache_drain(page, queue->pf_cache.pagecnt_bias);
- queue->pf_cache.va = NULL;
- }
-
+ page_frag_cache_clear(&queue->pf_cache);
noreclaim_flag = memalloc_noreclaim_save();
sock_release(queue->sock);
memalloc_noreclaim_restore(noreclaim_flag);
diff --git a/drivers/nvme/target/tcp.c b/drivers/nvme/target/tcp.c
index 66e8f9fd0ca7..ae871c31cf00 100644
--- a/drivers/nvme/target/tcp.c
+++ b/drivers/nvme/target/tcp.c
@@ -1438,7 +1438,6 @@ static void nvmet_tcp_free_cmd_data_in_buffers(struct nvmet_tcp_queue *queue)

static void nvmet_tcp_release_queue_work(struct work_struct *w)
{
- struct page *page;
struct nvmet_tcp_queue *queue =
container_of(w, struct nvmet_tcp_queue, release_work);

@@ -1460,9 +1459,7 @@ static void nvmet_tcp_release_queue_work(struct work_struct *w)
if (queue->hdr_digest || queue->data_digest)
nvmet_tcp_free_crypto(queue);
ida_free(&nvmet_tcp_queue_ida, queue->idx);
-
- page = virt_to_head_page(queue->pf_cache.va);
- __page_frag_cache_drain(page, queue->pf_cache.pagecnt_bias);
+ page_frag_cache_clear(&queue->pf_cache);
kfree(queue);
}

diff --git a/include/linux/gfp.h b/include/linux/gfp.h
index 65a78773dcca..5e15384798eb 100644
--- a/include/linux/gfp.h
+++ b/include/linux/gfp.h
@@ -313,6 +313,7 @@ static inline void *page_frag_alloc(struct page_frag_cache *nc,
{
return page_frag_alloc_align(nc, fragsz, gfp_mask, ~0u);
}
+void page_frag_cache_clear(struct page_frag_cache *nc);

extern void page_frag_free(void *addr);

diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h
index 0722859c3647..49a70b3f44a9 100644
--- a/include/linux/mm_types.h
+++ b/include/linux/mm_types.h
@@ -420,18 +420,13 @@ static inline void *folio_get_private(struct folio *folio)
}

struct page_frag_cache {
- void * va;
-#if (PAGE_SIZE < PAGE_FRAG_CACHE_MAX_SIZE)
- __u16 offset;
- __u16 size;
-#else
- __u32 offset;
-#endif
+ struct folio *folio;
+ unsigned int offset;
/* we maintain a pagecount bias, so that we dont dirty cache line
* containing page->_refcount every time we allocate a fragment.
*/
- unsigned int pagecnt_bias;
- bool pfmemalloc;
+ unsigned int pagecnt_bias;
+ bool pfmemalloc;
};

typedef unsigned long vm_flags_t;
diff --git a/mm/page_frag_alloc.c b/mm/page_frag_alloc.c
index bee95824ef8f..9b138cb0e3a4 100644
--- a/mm/page_frag_alloc.c
+++ b/mm/page_frag_alloc.c
@@ -16,88 +16,95 @@
#include <linux/init.h>
#include <linux/mm.h>

-static struct page *__page_frag_cache_refill(struct page_frag_cache *nc,
- gfp_t gfp_mask)
+/*
+ * Allocate a new folio for the frag cache.
+ */
+static struct folio *page_frag_cache_refill(struct page_frag_cache *nc,
+ gfp_t gfp_mask)
{
- struct page *page = NULL;
+ struct folio *folio = NULL;
gfp_t gfp = gfp_mask;

#if (PAGE_SIZE < PAGE_FRAG_CACHE_MAX_SIZE)
- gfp_mask |= __GFP_COMP | __GFP_NOWARN | __GFP_NORETRY |
- __GFP_NOMEMALLOC;
- page = alloc_pages_node(NUMA_NO_NODE, gfp_mask,
- PAGE_FRAG_CACHE_MAX_ORDER);
- nc->size = page ? PAGE_FRAG_CACHE_MAX_SIZE : PAGE_SIZE;
+ gfp_mask |= __GFP_NOWARN | __GFP_NORETRY | __GFP_NOMEMALLOC;
+ folio = folio_alloc(gfp_mask, PAGE_FRAG_CACHE_MAX_ORDER);
#endif
- if (unlikely(!page))
- page = alloc_pages_node(NUMA_NO_NODE, gfp, 0);
-
- nc->va = page ? page_address(page) : NULL;
+ if (unlikely(!folio))
+ folio = folio_alloc(gfp, 0);

- return page;
+ if (folio)
+ nc->folio = folio;
+ return folio;
}

void __page_frag_cache_drain(struct page *page, unsigned int count)
{
- VM_BUG_ON_PAGE(page_ref_count(page) == 0, page);
+ struct folio *folio = page_folio(page);

- if (page_ref_sub_and_test(page, count - 1))
- __free_pages(page, compound_order(page));
+ VM_BUG_ON_FOLIO(folio_ref_count(folio) == 0, folio);
+
+ folio_put_refs(folio, count);
}
EXPORT_SYMBOL(__page_frag_cache_drain);

+void page_frag_cache_clear(struct page_frag_cache *nc)
+{
+ struct folio *folio = nc->folio;
+
+ if (folio) {
+ VM_BUG_ON_FOLIO(folio_ref_count(folio) == 0, folio);
+ folio_put_refs(folio, nc->pagecnt_bias);
+ nc->folio = NULL;
+ }
+
+}
+EXPORT_SYMBOL(page_frag_cache_clear);
+
void *page_frag_alloc_align(struct page_frag_cache *nc,
unsigned int fragsz, gfp_t gfp_mask,
unsigned int align_mask)
{
- unsigned int size = PAGE_SIZE;
- struct page *page;
- int offset;
+ struct folio *folio = nc->folio;
+ size_t offset;

- if (unlikely(!nc->va)) {
+ if (unlikely(!folio)) {
refill:
- page = __page_frag_cache_refill(nc, gfp_mask);
- if (!page)
+ folio = page_frag_cache_refill(nc, gfp_mask);
+ if (!folio)
return NULL;

-#if (PAGE_SIZE < PAGE_FRAG_CACHE_MAX_SIZE)
- /* if size can vary use size else just use PAGE_SIZE */
- size = nc->size;
-#endif
/* Even if we own the page, we do not use atomic_set().
* This would break get_page_unless_zero() users.
*/
- page_ref_add(page, PAGE_FRAG_CACHE_MAX_SIZE);
+ folio_ref_add(folio, PAGE_FRAG_CACHE_MAX_SIZE);

/* reset page count bias and offset to start of new frag */
- nc->pfmemalloc = page_is_pfmemalloc(page);
+ nc->pfmemalloc = folio_is_pfmemalloc(folio);
nc->pagecnt_bias = PAGE_FRAG_CACHE_MAX_SIZE + 1;
- nc->offset = size;
+ nc->offset = folio_size(folio);
}

- offset = nc->offset - fragsz;
- if (unlikely(offset < 0)) {
- page = virt_to_page(nc->va);
-
- if (page_ref_count(page) != nc->pagecnt_bias)
+ offset = nc->offset;
+ if (unlikely(fragsz > offset)) {
+ /* Reuse the folio if everyone we gave it to has finished with it. */
+ if (!folio_ref_sub_and_test(folio, nc->pagecnt_bias)) {
+ nc->folio = NULL;
goto refill;
+ }
+
if (unlikely(nc->pfmemalloc)) {
- page_ref_sub(page, nc->pagecnt_bias - 1);
- __free_pages(page, compound_order(page));
+ __folio_put(folio);
+ nc->folio = NULL;
goto refill;
}

-#if (PAGE_SIZE < PAGE_FRAG_CACHE_MAX_SIZE)
- /* if size can vary use size else just use PAGE_SIZE */
- size = nc->size;
-#endif
/* OK, page count is 0, we can safely set it */
- set_page_count(page, PAGE_FRAG_CACHE_MAX_SIZE + 1);
+ folio_set_count(folio, PAGE_FRAG_CACHE_MAX_SIZE + 1);

/* reset page count bias and offset to start of new frag */
nc->pagecnt_bias = PAGE_FRAG_CACHE_MAX_SIZE + 1;
- offset = size - fragsz;
- if (unlikely(offset < 0)) {
+ offset = folio_size(folio);
+ if (unlikely(fragsz > offset)) {
/*
* The caller is trying to allocate a fragment
* with fragsz > PAGE_SIZE but the cache isn't big
@@ -107,15 +114,17 @@ void *page_frag_alloc_align(struct page_frag_cache *nc,
* it could make memory pressure worse
* so we simply return NULL here.
*/
+ nc->offset = offset;
return NULL;
}
}

nc->pagecnt_bias--;
+ offset -= fragsz;
offset &= align_mask;
nc->offset = offset;

- return nc->va + offset;
+ return folio_address(folio) + offset;
}
EXPORT_SYMBOL(page_frag_alloc_align);

@@ -124,8 +133,6 @@ EXPORT_SYMBOL(page_frag_alloc_align);
*/
void page_frag_free(void *addr)
{
- struct page *page = virt_to_head_page(addr);
-
- __free_pages(page, compound_order(page));
+ folio_put(virt_to_folio(addr));
}
EXPORT_SYMBOL(page_frag_free);

Next message: David Howells: "[PATCH net-next v5 05/19] tcp: Support MSG_SPLICE_PAGES"
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Next in thread: Jakub Kicinski: "Re: [PATCH net-next v5 03/19] mm: Make the page_frag_cache allocator use multipage folios"
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